The present invention relates to processes of the absorptive treatment of gas for the removal of hydrogen sulfide, and may find application in the petroleum, gas, petroleum-processing and chemical fields of industry.
Absorbents are known which may be used to remove hydrogen sulfide from gas, the absorbent comprising an aqueous solution of a hydroxide of iron. The principal disadvantage of this absorbent is the relatively low rate of regeneration. Another composition used to remove hydrogen sulfide from gas is disclosed in U.S. Pat. No. 4,515,764, issued May 7, 1985 to Diaz. This composition contains a polyvalent metal (e.g., iron) chelate of nitrilotriacetic acid, phosphate and thiosulphate ions. Also, U.S. Pat. No. 4,532,118, issued Jul. 30, 1985 to Tajiri et al., discloses the removal of H.sub.2 S from gas using a solution comprising ferric and ferrous ions, and ethylenediaminetetraacetic acid (EDTA) or a salt of EDTA, or triethanolamine (TEA) or a salt of TEA. Both of these U.S. patents are incorporated by reference herein in their entirety.
From the point of view of its technical essence and the result obtained, the absorbent suitable for the removal of hydrogen sulfide from gases which comes closest to the absorbent of the invention described herein comprises an aqueous solution of chelated iron, organic amine, and a hydroxide or carbonate of an alkali metal, in the following amounts, expressed as g/l:
______________________________________ Chelated iron (as calculated 0.1-50 for iron content) Organic amine 1-250 Hydroxide of alkali metal up to a Ph of 10 Water up to 1 liter ______________________________________
U.S. Pat. No. 4,036,942, issued Jul. 19, 1977 to Sibeud et al, discloses a process for removing hydrogen sulfide and alkyl mercaptans from fluid streams by reaction with oxygen in the presence of a metal amino acid chelate in aqueous solution containing an amine, converting hydrogen sulfide to sulfur and alkyl mercaptans to dialkyl disulfides, and separating these from the aqueous metal chelate solution. The solution may also contain an amine such as lower, water soluble aliphatic, alicyclic or heterocyclic amines. Examples of such amines include triethanolamine.
The principal disadvantage of this absorbent consists of its high corrosive activity, up to 3 m/year, at 50.degree. C.